Description: For any set-like well-ordered class, if the order isomorphism exists (is
a set), then it maps some ordinal onto A isomorphically. Otherwise,
F is a proper class, which implies that either ran F C_ A is a
proper class or dom F = On . This weak version of ordtype does
not require the Axiom of Replacement. (Contributed by Mario Carneiro, 25-Jun-2015)